The present invention relates to mobile sewer cleaning machines and, more particularly, to protection apparatus for shielding a high pressure hose wound on a reel and a sensor for determining when the reel produces excess slack in the hose.
The preferred embodiment of the invention is a component of a mobile sewer cleaning machine that is mounted on a truck body. Machines of this type have been proposed earlier. In many earlier machines, a hose is coiled or wound on a reel that extends transversely in a compartment at one side of the rear of the truck body. A control panel for controlling the reel drive is mounted on the rear of the machine at the other side. An example of such machine is disclosed in U.S. Pat. No. 3,774,630, issued Nov. 27, 1973.
In sewer cleaning systems of this general type, a length of hose is unwound from the reel at the rear of the truck into a sewer. The reel is rotated by a motor which is controlled by the operator standing at the control panel along side the hose. The end of the hose carries a jet nozzle which pulls itself and the hose through the sewer by the force of its rearwardly directed, high pressure water jets, while at the same time washing the debris in the sewer back toward the manhole.
After the nozzle has traveled for a distance through the sewer pipe, the motor connected to the reel is reversed to rewind the hose onto the reel. As the nozzle travels back towards the manhole, the sewer debris is washed ahead of it in the same direction. This process is repeated several times until the length of sewer pipe is cleaned. Because of sharp, abrasive debris in the sewer pipes, hoses become worn out and damaged by this process. If the damage is discovered, the hose is repaired by cutting out the damaged portion and splicing it back together with a fitting. Even though the hose has been repaired, the splice represents a weak spot in the hose. In any event, the water is supplied to the hose at an extremely high pressure, on the order of 2,000 p.s.i., during the process. Such a high pressure can cause a damaged or repaired hose to rupture and burst. If the hose should burst at a point close to the operator, there is substantial possibility of serious injury. Operators have actually been killed by this kind of accident.
Another problem encountered with known sewer cleaning equipment of this type is the tangling which may occur in the hose. This may occur due to the operator standing in a position where he cannot see the hose unwinding, or simply because the operator is not paying attention to the hose. As the nozzle pulls and advances the hose through the sewer line, the hose is unwound from the reel by the motor, the speed and direction of which are controlled by the operator. During this time, the nozzle may encounter a substantial amount of refuse and debris in the sew pipe which momentarily hinders the advancement of the hose. If the operator is aware of the situtation, he monitors the progress of the hose by looking down into the sewer and appropriately adjusts the speed of the motor to match the progress of the nozzle through the sewer. When the operator looks down into the sewer, the operator's view is often obstructed by the steam rising out of the sewer. This is compounded during cold weather when the steam condenses and further obstructs the operator's view. If, on the other hand, the operator does not notice this and reduce the speed of rotation of the reel, the reel will unwind the hose faster than it is being advanced by the nozzle and produce an excess slack of hose. This excess slack in the hose will initially be manifested by a loop of hose descending to the floor of the reel compartment, eventually buckling back within the compartment and possibly becoming wedged or entangled therein.
Accordingly, there is a need for protection apparatus to shield an operator from a bursting hose and to sense when rotation of the reel produces excess slack in the hose.